Cathodic Protection of

Concrete Structures

Systems By SRCP

Cathodic Protection Systems• Impressed Current

• Zebra• Cassette• CorroDisc Surface Embedded

• Sacrificial Anode• ZLA• Roll Anode• GSC Super Anode• Clip On Anode

• Monitoring and Control • Camur

Conductive coatingSurface mounted ribbon anodeMesh in precast stick-on shapes Ti wire in acid resistant cylinder for embedment

Zinc sheet with self adhesive activatorRolled ZLA grouted in drill holeZLA block for embedment in repairZLA block in precast container

Remote monitoring and control

Reinforcement Corrosion Process

Corrosion Reaction

CathodicReaction

2(OH)-

AnodicReaction

SecondReaction

H2O

Fe(OH)2

O2

Fe++ 2e-

WaterChloride Oxygen

Fe2O3H2O(Rust)

H2O ½O2

Rebar

OxygenAn area of reinforcement becomes anodic due to chloride or carbonation ingress.Corrosion is stopped if:• Oxygen at cathode

stopped• Full immersion• Small cathode

• Resistance of electrolyte high• Low due to chloride

& water• Electrons supplied from

alternative anode

Anodic and cathodic reaction are critical to how the cell works.

What is Cathodic Protection• Provides and alternate anode to prevent reinforcement corrosion

• Sufficient current to ensure protection over all rebar• Determined by code criteria

• 100mv decay at 24hrs• Eliminates need for breakout of sound but contaminated concrete• Eliminates structural problems

• Reduced noise and dust

Galvanic Anode

Curr

ent

C u r r e n t F l o w

Impressed Current Cathodic Protection• Powered system so no limit to the level of protection• Over protection

• Prestress particular concern

• Acidification around anode possible

• Under protection• System failure• Protection requirements change

• Reliable and total protection when maintained

• Detailed design • Expert commissioning• Regular monitoring

• High life cycle cost• Particularly for small projects

Zebra

Zebra Anode

Zebra PDR TapeZebra PDR

Concrete

Wearing Surface

Bond Coats

Layers of a Zebra System for the wearing surface of a car park deck

US Patent 6855199 B1 2005• Water soluble silicate carrier

• penetrates and forms micro-crystalline bond with concrete

• Filled graphite particles

ZebraProjects• 400+ projects • Light weight• Conventional painting skills

• Rapidly applied• Decorative• 20+ year lifeApplications

• Building facades, balconies and slabs.

Building facade Car park capillary rise zone

Balcony soffits Car park slab

Cassette• Ribbon anode in a surface mounted inert carrier.

• Ribbon anodes are a proven ICCP system except acidification of slotted systems can cause failure after 15-20 years.

• Cassette overcomes acidification issues.

10mm Stainless Steel Bolt

Inert Fibreglass Panel

Glasswool Contact Pad

Elgard 150 Ribbon Anode

80x80 mm HDG washer Isolating Washer

22mm long Glass Fibre Nut/washer

15mm diameter hole drilled in concrete

Polyester resin , e.g. Ramset Chemset 101 or similar

Fibre Glass Plate 80x80x9.5mm with 18mm diameter central hole

40m

m

½”ø 100mm long Glass FibreStud

25mm

Cassette• Proven Elgard 150 ribbon anode.• Surface mounted in own tray. No grinding or shotcrete.• Inert system. Acidification around anode not an issue.• Simple to install. Just bolt on (stainless steel or fibre glass).

• Doesn’t add significant weight. • MMO coated titanium, life typically 50 years.Applications

• Where aesthetics not critical, e.g. tanks, car parks• Confined spaces, e.g. basements, tunnels• Projects where wet exposure, wharf and bridges splash zones

Cassette ProjectsPipe tunnel, poor access

Prestressed bridge T-Roffs

Car park capillary rise area

Cast insitu bridge beam

Roof of Tunnel Soffit Brdige deck soffit

CorroDisc• MMO coated titanium mesh in a silicate based mortar• Mesh

• long term proven performance• 50 year life

• Mortar • resistant to strong acids• Permeable to water vapour &

oxygen• Real CP

• Satisfies the 100mV criteria• Convenient testing

• Use individual Corrodisc anodes

CorroDisc 125 – 125mm diameter circular surface applied anode typically applied on a rectangular grid to give 4-8 anodes/m2

CorroDisc R – 60x400mm wide surface applied anode typically applied in line to give 3-4 anodes/m2

MMO coated

titanium mesh

CorroDisc• Easy & economic installation

• Surface applied• Avoids grinding, drilling or embedding the anodes in the structure

• Local surface preparation only

• Flexible anode placement

• Reasonable appearance once coated

• Not suited to wet areas

Pressing CorroDisc R onto surface

Pressing CorroDisc 125 onto surface

Camur Monitoring and Control• Remote control & monitoring essential for ICCP

• Power supply units 3 or 8amp

• Single bus cable• Power control • Power monitoring• Half cell monitoring

• Integral computer logs data

• Data accessed remotely• Data collection software• Web viewing software

Bus interface

Computer

1 zone system (Available for control and monitoring of trial areas).

Transformer

Rectifier

Camur• Camur System• IP box• Computer• Transformer• Fix Volts• Transformer• Bus Interface• Light/fan/heater

• Fuses/sockets• Connectors• Software• Web Site

Concrete Structure

220/240V Power

Supply

Control Cabinet

Gen. Skt 1 (e.g. Insp. Comp.)1

Cabinet Fuse1

9m max1.7m max

Anode Wire Grid

Bus

P-Node

120ohm

120ohm

P-Node

P-Node

P-Node

P-Node

P-Node

Anode Zone 3

Anode Zone 2Anode Zone 1

Transformer for each Fix Volta)so Fix Volt is all

low voltb)to eliminate

ground loops

Fix Volt Fix VoltFix Volt

Bus (plug together)

4 or 8 Amp

24V AC

Anode Zone 1

Power Term.4

Sensor wires5

Anode Zone 2

Anode Zone 3

Comp. Skt

Gen. Skt 2 (e.g. GSM)Fuse All

other than Gen. Skt. 11

Heater2

Light/ /Heat/ Fan Fuse

FanThermostate2

Thermo-stat2

GSM (USB)

Screen (HDMI)

Keyboard (USB)

Client Supplied

Network (LAN port)Bus (USB)

24V

DCBu

s Tra

nsfo

rmer

Bus Interface3

Controller

3 zone system with all anode beds in same location.

Concrete Structure

220/240V Power

Supply

Concrete Structure

Transformer for each Fix Volta)so Fix Volt is all

low voltb)to eliminate

ground loops

Fix Volt Fix Volt

Bus (plug together)

4 or 8 Amp

24V AC

Anode Zone 1

Power Term.

Sensor Term.

Anode Zone 2

Transformer Fuse

Bus

9m max1.7m max

Anode Wire Grid

P-Node

120ohm

P-Node

P-Node

P-Node

Anode Zone 2Anode Zone 1

W-Node

Area 7*3*1.7m*1.9m =

Approx.320m2

Typically max around 500m2 but

could be much lower with high density steel

Strips 500-600

wide with 50mm

gaps

GSM (USB)

Control Cabinet 1

Controller

Bus (USB)

Cabinet Fuse1

Gen. Skt 1 (e.g. Insp. Comp.)1

Screen (HDMI)

Keyboard (USB)

Gen. Skt 2 (e.g. GSM)

Comp. Skt

24V

DCBu

s Tr

ansf

orm

er

Client Supplied

Light/ /Heat/ Fan Fuse

Fuse All other than

Gen. Skt. 11

Fan

Heater2

Thermostate2

Thermo-stat2

Network (LAN port)

Fix Volt

P-Node

P-Node

Anode Zone 3

Fuse All

120ohm

Bus

Tran

sfor

mer

24V DC

Cabinet Fuse

W-Node

120ohm

120ohm

Gen. Skt (e.g. Insp. Comp.)1

Aux Cab.

Anode Zone 3

2 Zones 3 Zones

Right: 3 zone system where anode beds separated. Note wireless link of bus cable.

Camur

Working systems.

Concrete Structure

• Components sold individually

• Computer• Transformer

• Fix Volts• Transformer

• Bus Interface

ZLA Range of Sacrificial Anodes• High output for true cathodic protection• Simple to install; limited wiring, no power source• Doesn’t add significant weight. Decorative after coating.

• Low design; installation and monitoring costs• Zinc consumed, life typically 20 yearsApplications

•Low cost or limited life projects•Applicators not expert in cathodic protection•Holding repairs•Prestressed items

Cathodic Protection vs Prevention+400

0

-400

-800

-12000 0.5 1.0 1.5 2.0

Pote

ntia

l (m

V vs

SC

E)

Chloride Content (wt % cement)

PittingCondition conducive to stable propagation of pits

Perfect Passivity

Allows pre-existing pits may propagate but new pits unlikely

Imperfect Passivity

Hydrogen DischargeOxide unstable, hydrogen formed cathodically

A

B C

D

E

F

Cathodic Prevention

Cathodic Protection

Initiation and propagation of pits inhibited

A small potential shift gives cathodic prevention, i.e. a high chloride corrosion threshold for cathodic steel. Use low output anodes for incipient anode protections.A large potential shift gives cathodic protection, i.e. immunity from corrosion for active steel. Use high out put anodes (ZLA range) for true CP and no breakout.

SACP systems must provide 100mv 24hr potential decay criteria

Cyclic Voltametric Testing• Standard electrode test procedure• Cycle voltage and measure current

• Zinc Activator Paste (ZAP) optimised by CVT trials

Cat

hode

Cur

rent

Den

sity

[mA/

100c

m2 ]

Polarisation [mV Ag/AgCl]

0.01

0.1

10

100

1

-800 -600 -400 -200

Zinc in LiOH based mortar

Expected Polarisation

Steel

Current for 0.167mv/s sweep rate

ZAP outputLiOH output

Intersection of steel and anode tests gives polarisation expected from anode

Test system set up

Zinc Layer Anode (ZLA)• Zinc in contact with concrete passivates• Activator applied to zinc keeps it active and ensures continuous cathodic protection

• Reactions at the anode / activator interface critical• Zinc chloride formed with ZLA anodes gives high output and long term performance

• Anodes lead to true CP with meeting 100mv 24hr decay criteria

Roll Anode and GSC Super Anode derived for ZLA and both give CP meeting 100mv criteria.

Roll of ZLA as applied to the

surface of concrete to

provide full CP meeting 100mv

criteria

ZLA Projects

Balconies Walkways Facades Bridges

After ZLA Application

After Coating

Roll Anode• Drill hole

• Depth to move away from extreme fibre stress as required

• Insert anode and grout• ZAP for best CP performance

• Cement grout for strength

Anode string connected to rebar

27mm diameter Roll Anode

Typical Roll Anode Installation

GSC Super Anode• Bolt to rebar• Cast into repair• Cathodic Protection

• No breakout behind bars

• Incipient anode protection Anode

string connected to rebar

30/20 GSC Super Anode

SACP Performance Data• Seineflat Apartments• 100mv criteria met at installation and after 2 years

SACP Performance Data• Cape Perpetua Viaduct• 100mv criteria met at installation and after 5 years

0 1 2 3 4 5Time (Hours)

300

200

100

0

Pote

ntia

l Dec

ay (m

v C

SE)

Installed 1998

April 2002

Jan 2003

SACP• Stockton Bridge Trial

• ZLA provides three times the polarisation of the other SA anodes

1

2

3

1.5m

1.7m

Ref Cell

123

Potential (mV vsAg/AgCl) Before

Connecting Anode-87mV -25mV-22mV

Potential mV vsAg/AgCl 2-3min After Connecting

Anode-393-609-602

Current (mA) 3-4min After Connecting

Anode

22

Voltage (mV) 2-3min After Connecting

Anode

0.987

Anode

ZLA

Inst. Off

-476-416-469

24hr off-58-50-18

24hr decay418366451

Monitoring results 23/1/13 (mv)

CM2 Rebar Continuity

• ICCP and SACP wont work if there is not rebar continuity

• CM2 Continuity Tester measures :

• resistance at high current (1 Amp) to test connection under load. This is a common failure of connections tested with standard voltmeters. Criteria ≤1ohm)

• residual voltage 0.1 sec after the resistance test. Criteria =0V